It is recognized that numerous pathogens are present on human skin. Therefore, in a hospital environment, it is generally desired that the growth of disease-producing microorganisms be inhibited, and preferably that these microorganisms be destroyed so as to control patient infection and encourage wound healing. Under most circumstances, the bacteria of normal skin cannot cause wound infections, but in the presence of foreign materials or open wounds, the pathogenic potential of these bacteria appears to be considerably enhanced. Furthermore, the likelihood of bacterial contamination is at a peak immediately preceding, during, and following surgical procedures. Accordingly, to prevent contamination, it is imperative that the skin be effectively disinfected before a surgical incision is made and during the entire surgical procedure.
In response to such concerns, many topical antimicrobial agents have been developed. These agents typically are in the form of preoperative skin preps, surgical scrub tissues, washes, wound cleaners, lotions and ointments. A recognized limitation to such topical applications are a short effective delivery time. Microorganisms that may have survived the initial application of such a topical antimicrobial agent can act as a seed, causing the pathogen population in some instances to regenerate or rise to their initial levels. Thus, continuous application of an antimicrobial agent to the site is recognized as a means of inhibiting this increase in population.
It has been recognized that a continuous or longer lasting antimicrobial effect may be achieved by incorporating the antimicrobial agent into an adhesive layer or into a surgical incise drape material itself.
Berglund et al. (U.S. Pat. No. 4,310,509) disclose that it is known to incorporate biologically active agents into adhesive layers on a substrate to provide continuous application of such agent to the body. Disclosed examples of known adhesives containing antimicrobial agents include U.S. Pat. No. 2,137,169, wherein phenol, thymol, methanol, etc. are added to a starch adhesive; U.S. Pat. No. 3,249,109 where benzocaine was added to a tacky gelatin; U.S. Pat. No. 3,632,740 where a corticosteroid is added to an adhesive; U.S. Pat. No. 3,734,097 where a microencapsulated anti-neoplastic agent is added to an adhesive; U.S. Pat. No. 4,073,291 where Tretinoin is added to an adhesive; U.S. Pat. No. 3,769,071 where 5-fluorouracil is incorporated into an adhesive; and U.S. Pat. No. 3,896,789 where retinoic acid is incorporated into a pressure-sensitive adhesive tape. Berglund et al. further teach that the prior art attempts to include an antimicrobial agent in an adhesive did not include the use of a broad spectrum antimicrobial because such adhesives had been frustrated by uncontrollable release of the agent with accompanying skin irritation in some patients, along with failure to obtain sufficient antimicrobial activity.
Berglund et al. disclose a pressure sensitive adhesive composition which contains chlorhexidene, polyvinylpyrrolidone iodine or iodine which is applied onto a polymer sheet material, such as polyethylene or polyurethane, for use as a surgical drape. The disclosed drape is applied to the skin with the adhesive side contacting the skin so that the antimicrobial agent can be released from the adhesive to the wound area prior to and during incision. The process for making the adhesive disclosed by Berglund et al. involves forming an emulsifiable concentrate or an organic solution concentrate of a broad spectrum antimicrobial agent and mixing it into an adhesive, such that the broad spectrum antimicrobial is homogeneously dispersed as a separate phase throughout the adhesive medium. The homogenous dispersion is then spread or coated to a substantially uniform layer followed by drying of the wet layer in order to remove the solvents.
Rosso et al. (U.S. Pat. No. 4,323,557) disclose a drape incorporating a pressure sensitive adhesive utilizing n-vinylpyrrolidione residues in the polymer backbone. Iodine is complexed with these residues to provide an antimicrobial effect. Rosso et al. espouse the stability of the adhesive composition over the prior art compositions. By stable, Rosso et al. asserts that a composition coating of 11 grains per 24 sq. in. which is attached to a polyethylene sheet can be exposed to a temperature of 120.degree. F. and a relative humidity of 9% for two weeks or to a dose of 2.5 megarads of gamma irradiation without substantial alteration of the physical appearance or of the chemical activity as tested by the starch test and microbiological activity as tested by the zone inhibition assay. The disclosure of Rosso et al. is incorporated herein by reference.
The process for forming the adhesive composition disclosed by Rosso et al. involves forming a pressure-sensitive adhesive and mixing into it an antimicrobial treating solution comprising iodine, an iodide, and a solvent. The resulting composition preferably contains n-vinylpyrrolidone in the backbone of the pressure-sensitive adhesive which serves to complex the iodine. Rosso et al. disclose that the composition may be either attached directly onto a flexible backing substrate or formed onto a release liner for later use. Once applied, the solvents are then evaporated by means known to the art, whereby an adhesive film is formed which is useable in or on tapes, drapes and other medical devices.
Mixon et al. (U.S. Pat. No. 5,069,907) disclose a surgical drape having incorporated therein a broad spectrum antimicrobial agent. The drape comprises a synthetic polymeric film or fabric having incorporated therethrough an amount of antimicrobial agent. The drape may optionally have an adhesive layer attached to one of its external surfaces, wherein the adhesive layer can have dispersed therethrough an antimicrobial agent. The preferred antimicrobial agent used is 5-chloro-2-(2,4-dichlorophenoxy)phenol. Suitable adhesives utilized include polyacrylate adhesives.
Mixon et al. disclose a large number of antimicrobial agents which were contemplated for use with the disclosed composition. These include metal salts, typical antibiotics, antibacterial agents such as chlorhexidine and its salts, quaternary ammonium compounds, iodophors such as povidone iodine, acridine compounds, biguanidine compounds, and a preferred antimicrobial agent 5-chloro-2-(2,4-dichlorophenoxy)phenol. Mixon et al. further disclose that these same antimicrobial agents, which they propose to utilize within the polymer composition for their surgical drape, can also be utilized in an adhesive composition. Mixon et al. further state that the antimicrobial agent can be directly applied to the surgical drape in solution as an aqueous dispersion, as a hot melt, or by a transfer process using known techniques, such as knife, roller-coating, or curtain-coating methods. The transfer process is disclosed as particularly preferred. In a transfer process, the adhesive emulsion, including water or a different solvent, optionally containing an antimicrobial agent, is spread onto a sheet of release paper and dried to remove the water or solvent. The surgical drape is then brought into contact with the adhesive and calendared to insure that the adhesive adheres to the drape. The surgical drape will then generally include a release sheet covering the adhesive, and the release sheet on which the adhesive is deposited can be used for that purpose, or that release sheet can be removed and replaced with another release sheet. In embodiments where the adhesive contains an antimicrobial agent, the mixture of adhesive and antimicrobial agent is dried after coating on the release sheet, and the antimicrobial agent remains dispersed in the adhesive.
Generally, presently known antimicrobial agents are limited in their ability to withstand heat during processing. The lack of heat stability of n-vinyl pyrrolodione iodine has limited the ability for drapes having this antimicrobial agent from being ethylene oxide sterilized under heat stress. Further, many of the antimicrobial compounds cannot be radiation sterilized. Thus, each prior art reference teaches that it is preferred to apply the antimicrobial adhesive in conjunction with a solvent followed by subsequent evaporation of the solvent.
Accordingly, the need exists for an adhesive composition having an antimicrobial agent dispersed therethrough which is heat stable and solventless. Such composition would eliminate the need for use of solvents with their potential environmental effects and would eliminate the need for removing such solvent from the adhesive after application to the drapes. Further, the heat stability would allow the solventless adhesive to be applied in a hot melt process, while also allowing for ethylene oxide sterilization under heat stress or radiation sterilization.